MUSCLES OF THE TRUNK AND SHOULDER

Muscles of the Body Skeletal muscles Produce movements Blinking of eye, standing on tiptoe, swallowing food, etc. General principles of leverage Muscles act with or against each other Criteria used in naming muscles

Lever Systems: Bone-Muscle Relationships Movement of skeletal muscles involves leverage Lever – a rigid bar that moves Fulcrum – a fixed point Effort – applied force Load – resistance

Lever Systems Figure 11.1a

Lever Systems Figure 11.1b

Lever Systems: Bone-Muscle Relationships Bones – act as levers Joints – act as fulcrums Muscle contraction – provides effort Applies force where muscle attaches to bone Load – bone, overlying tissue, and anything lifted

Lever Systems: Bone-Muscle Relationships Levers allow a given effort to Move a heavier load Move a load farther Mechanical advantage Moves a large load over small distances Mechanical disadvantage Allows a load to be moved over a large distance

Lever Systems: Bone-Muscle Relationships First-class lever Effort applied at one end Load is at the opposite end Fulcrum is located between load and effort

Lever Systems: Bone-Muscle Relationships Examples – seesaws, scissors, and lifting your head off your chest Figure 11.2a

Lever Systems: Bone-Muscle Relationships Second-class lever Effort applied at one end Fulcrum is at the opposite end Load is between the effort and fulcrum Examples – wheelbarrow or standing on tiptoe An uncommon type of lever in the body Work at a mechanical advantage

Lever Systems: Bone-Muscle Relationships Figure 11.2b

Lever Systems: Bone-Muscle Relationships Third-class lever Effort is applied between the load and the fulcrum Work speedily Always at a mechanical disadvantage Figure 11.2c

Lever Systems: Bone-Muscle Relationships Most skeletal muscles are third-class levers Example – biceps brachii Fulcrum – the elbow joint Force – exerted on the proximal region of the radius Load – the distal part of the forearm

MUSCLES OF THE LIMBS

Muscle Compartments of the Limbs Dense fibrous connective tissue divides limb muscles into compartments Muscles in opposing compartments are Agonist and antagonist pairs Each compartment is innervated by a single nerve

Muscle Compartments of Arm and Forearm The upper limb has anterior and posterior compartments Anterior arm compartment muscles Flex the shoulder or arm Innervation is the musculocutaneous nerve Anterior forearm compartment muscles Flex the wrist and digits Innervation is the median or ulnar nerve

Muscle Compartments of the Arm and Forearm Figure 11.5a

Muscle Compartments of the Arm and Forearm Figure 11.5b

Muscles Crossing the Shoulder Joint Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings MuscleOriginInsertion FEAbAdMRLRNerve Supply Pectoralis Major Sternum & rib cart. 1- 6, prox. clavicle, ext. oblique aponeurosis Great tubercle of humerus XXX Lateral & Medial Pectoral n. (C5-T1) Deltoid Lateral clavicle, scapular acromion & scapular spine Deltoid tuberosity of humerus X Axillary n. (C5-C6) Latissimus dorsi Spines of lower 6 thoracic vert., iliac crest, scapular inf. angle Intertubercular sulcus of humerus XYY Thoracodorsal n. (C6-C8) Teres major Scapular post. Inf. angle Lesser tubercle of humerus XXX Lower subscapular n Subscapularis Subscapular fossa of scapula Lesser tubercle of humerus X Subscapular n. (C5- C7) Supraspinatus Supraspinous fossa of scapula Greater tubercle of humerus (sup.) X Suprascapular n. Infraspinatus Infraspinous fossa of scapula Greater tubercle of humerus X Suprascapular n. Teres minor Lateral dorsal border of scapula Greater tubercle of humerus X Axillary n. Coracobrachialis Coracoid process of scapula Medial humeral shaft XX Musculocutaneous nerve Movements of the Arm (Humerus) ATTACHMENT MUSCLE ACTION (prime movers) X- arm (humerus) movement Y- shoulder movement

Figure 11.16a–b

Figure 11.15a

Figure 11.15b

Muscles Crossing the Elbow Joint Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Posterior MusclesOriginInsertion FEAbAdMRLRNerve Supply Triceps brachii Long head- infraglenoid scapular tubercle Lateral head- post. Humeral shaft Medial head- distal of radial groove Humeral olecranon process X Radial n. (C6-C8) Anconeus Lateral epicondyle of humerus Lateral aspect of olecranon process of ulna XY Radial n. (C6-C8) Biceps brachii Short head- coracoid process Long head- supraglenoid cavity and intertubercular sulcus Radial tuberosity X Musculocutaneous (C5-C6) Brachialis Anterodistal humerus embraces deltoid muscle insertion Coronoid process of ulna and elbow joint capsule X Musculocutaneous Brachioradialis Lateral supracondylar ridge distal humerus Styloid process of radius X Radial n. (only flexor muscle that it innervates) Flexion and extension of the forearm ATTACHMENT MUSCLE ACTION (prime movers) X- forearm movement Y- ulnar movement Anterior Muscles Supinates forearm

Muscles Crossing the Elbow Joint Figure 11.16a

Figure 11.16c

Figure 11.16d

Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 11.15c

Figure 11.15d

Muscles of the Forearm Movements of the wrist, hand, and fingers Tendons are anchored by Flexor and extensor retinacula Most forearm muscles arise from the distal humerus Movements at the wrist include Flexion, extension, abduction, and adduction Wrist and fingers are “operated” by muscles in the forearm

Muscles of the Forearm Flexors Anterior flexor compartment Innervated by median and ulnar nerves Originate from a common tendon Medial epicondyle of the humerus

Superficial Anterior Muscles of the Forearm Pronator teres Flexor carpi radialis Palmaris longus Flexor carpi ulnaris Flexor digitorum superficialis Figure 11.17a

Deep Anterior Muscles of the Forearm Flexor pollicis longus Flexor digitorum profundus Pronator quadratus

Deep Anterior Muscles of the Forearm Figure 11.17b, c

Muscles of the Forearm Carpometacarpophalangeal Joint Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings ANTERIOR COMPARTMENTOriginInsertion FEAbAdMRLRNerve Supply Pronator teres Medial epicondyle humerus; coronoid process ulna Lateral midshaft of radius X Median n. Flexor carpi radialis Medial epicondyle humerus 2 and 3 Metacarpal base WH Median n. Palmaris longus Medial epicondyle humerus Palmar aponeurosis WXWX Median n. Flexor carpi ulnaris Medial epicondyle of humerus; olecranon process & post. ulna Pisiform & hamate; 5 metacarpal base WH Ulnar n. (C7,C8) Flexor digitorum superficialis Medial epicondyle humerus; coronoid process ulna; radial shaft Middle phalanges 2-5 W P 2-5 Median n. (C7,C8,T1) Flexor pollicis longus Ant. Radius & interosseous memb Distal phalange 1 P1P1 Median n. branch (C8,T1) Flexor digitorum profundus Anteromedial ulna & interosseous memb Distal phalange 2-5 P 2-5 Ulnar n.- Medial half Median n.- Lateral half Pronator quadratusAnterodistal UlnaAnterodistal radiusMedian n. (C8,T1) Movements of the Wrist, Hand, and Fingers ATTACHMENT MUSCLE ACTION (prime movers) X- elbow movement H- hand movement W- wrist movement P- phalanges movement Deep Muscles Pronates forearm Superficial Muscles Tenses skin & fascia of palm Pronates forearm

Figure 11.17a

Figure 11.17b

Muscles of the Forearm Extensors Posterior compartment of the forearm Innervated by the radial nerve Originate at a common tendon Lateral epicondyle of the humerus

Muscles of the Forearm Carpometacarpophalangeal Joint Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings POSTERIOR COMPARTMENTOriginInsertion FEAbAdMRLRNerve Supply Brachioradialis Lateral supracondylar ridge distal humerus Styloid process of radius X Radial n. (only flexor muscle that it innervates) Extensor carpi radialis longus Lateral supracondylar ridge humerus Metacarpal base 2 WW Radial n. (C6,C7) Extensor carpi radialis brevis Lateral epicondyle humerus Metacarpal base 3 WW Radial n. (deep branch) Extensor digitorum Lateral epicondyle humerus Distal phalanges 2-5 WPWP P Radial n. (post. Interosseous n.; a branch of C5,C6 ) Extensor carpi ulnaris Lateral epicondyle humerus; post. ulna Metacarpal base 5 WW Radial n. (post. Interosseous n.) Supinator Lateral epicondyle humerus; prox. ulna Proximal radius Radial n. (post. Interosseous n.) Abductor pollicis longus Post. Radius/ulna; interosseous memb. Metacarpal base 1; trapezium P1P1 P1P1 Radial n. (post. Interosseous n.) Extensor pollicis brevis & longus Dorsal Radius/ulna; interosseous memb. Brevis- Prox. Phalange 1 Longus- Prox. Phalange 1 P1P1 Radial n. (post. Interosseous n.) Extensor indicis Posterodistal ulna; interosseous memb. Extensor digitorum joint P2WP2W Radial n. (post. Interosseous n.) Movements of the Wrist, Hand, and Fingers ATTACHMENT MUSCLE ACTION (prime movers) X- elbow movement H- hand movement W- wrist movement P- phalanges movement Deep Muscles Superficial Muscles Supinate forearm

Superficial Posterior Muscles of the Forearm Brachioradialis – flexes forearm Extensor carpi radialis longus Extensor carpi radialis brevis Extensor digitorum Extensor carpi ulnaris Figure 11.18a

Deep Posterior Muscles of the Forearm Supinator Abductor pollicis longus Extensor pollicis brevis and longus Extensor indicus Figure 11.18b

Figure 11.18a

Figure 11.17c

Figure 11.18b

Figure 11.18c

Intrinsic Muscles of the Hand Fine movement of the fingers All located in the palm Control precise movements Include muscles of Adduction, abduction, and opposition

Intrinsic Muscles of the Hand Thenar muscles – ball of thumb Abductor pollicis brevis Flexor pollicis brevis Opponens pollicis Adductor pollicis Hypothenar muscles Abductor digiti minimi Flexor digiti minimi Opponens pollicis PLAY Muscles that act on the wrist and fingers: an overview

Intrinsic Muscles of the Hand: Fine Movements of the Fingers Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings THENAR (BALL OF THUMB)OriginInsertion FEAbAdMRLRNerve Supply Abductor pollicis brevis Flexor retinaculum; nearby carpals Proximolateral phalange base 1 P1P1 Median n. (C8,T1) Flexor pollicis brevis Flexor retinaculum; nearby carpals Proximolateral phalange base 1 P1M1P1M1 Median n. (occas. Ulnar n.) Opponens pollicis Flexor retinaculum; trapezium Anterior side metacarpal 1 Median n. (occas. Ulnar n.) Adductor pollicis Metacarpal base 2-4; front metacarpal 3 Medioproximal Phalange 1 P1P1 Ulnar n. (C8,T1) Abductor digiti minimiPisiform bone Proximomedial Phalange 1 P5P5 Ulnar n. Flexor digiti minimi Flexor retinaculum; hamate Proximomedial Phalange 1 P5P5 Ulnar n. Opponens digiti minimi Flexor retinaculum; hamate Most medial metacarpal 5 Ulnar n. Lumbricals Lateral side Flexor Digitorum Profundus tendon Lateral extensor expansion first Phalange 2-5 P MCP P ICP Median n. (lateral 2) Ulnar n. (medial 2) Palmar interossei Metacarpal side midaxis of hand Extensor expansion Phalange 1 (1,2,4,5) midaxis of hand P 1-5 Ulnar n. Dorsal interosseiMetacarpal side Extensor expansion Phalange 1 (2-4) opposite side midaxis of hand (both side 3) P 1-5 Ulnar n. MUSCLES ATTACHMENTMUSCLE ACTION X- elbow movement H- hand movement W- wrist movement P- phalanges movement O- Opposition Opposition (P1 to P5) MIDPALMAR MUSCLES HYPOTHENAR (BALL OF LITTLE FINGER) Opposition (P1 to P5)

Intrinsic Muscles of the Hand Figure 11.19a

Intrinsic Muscles of the Hand Midpalmar muscles Lumbricals Palmar interossei Dorsal interossei Figure 11.19b

Figure 11.19c–d